A battery installed in, for example, a vehicle and a generator for charging the battery are connected through a charging cable. As conventional battery chargers capable of detecting a break in the charging cable, various types of them have been well known.
As one example of the conventional battery chargers, a voltage regulating apparatus for charging generators is disclosed in U.S. Pat. No. 4,618,811 corresponding Japanese Unexamined Patent Publication No. S59-148538. As another one example of the conventional batter chargers, a battery recharging system for a motor vehicle is disclosed in U.S. Pat. No. 5,151,646 corresponding to Japanese Unexamined Patent Publication No. H4-222426.
The voltage regulating apparatus disclosed in the former Publication is provided with a charging generator and a voltage regulator. The charging generator includes an AC (Alternating Current) generator and a rectifying circuit. The output terminal of the rectifying circuit is connected to a battery through a charging cable. The voltage regulator has L and S terminals, the L terminal of which is connected to the output terminal of the rectifying circuit, and the S terminal of which is connected to the positive terminal of the battery.
The voltage regulator regulates the output voltage of the charging generator based on the voltages at the L terminal and S terminal. The voltage regulator also determines that the charging cable has a break when the difference between the voltage at the L terminal and that at the S terminal exceeds a predetermined value, thereby stopping the operation of the charging generator and generating an alarm.
In addition, the battery recharging system for a vehicle disclosed in the later Publication includes a current generator, a switch, an indicator lamp, and a voltage regulator. The current generator includes an alternator and an associated rectifier whose output terminal is connected to the positive terminal of a battery through a connecting cable.
The voltage regulator is provided with first and second input terminals A and L, the first input terminal A of which is connected to the output terminal of the current generator, the second input terminal of which is connected the positive terminal of the battery through the switch and the lamp.
The voltage regulator regulates the output voltage of the current generator based on the potential at the first input terminal A and that of the second input terminal L. The voltage regulator also determines that the connecting cable has a break when the potential difference between the potential at the first input terminal A and that at the second input terminal L is greater than a pre-established reference value, thereby causing the lamp to be lit to indicate the interruption of connection between the battery and the current generator.
In order to reduce environmental pollution by vehicles and energy consumption thereby, vehicle control has been integrated. For example, when integrated vehicle control is applied to a battery charging system, the integrated vehicle control optimizes the alternator output when an engine runs at idle to regulate emissions. The integrated vehicle control also regulates the alternator output during acceleration and deceleration to control energy consumption of vehicle electric loads. This integrated vehicle control uses a plurality of ECUs (Electronic Control Units) as external control units, various sensors connected thereto, and actuators whose operations are controlled by the ECUs.
In order to achieve the efficient integrated vehicle control, there have been prepared a plurality of data communication control methods between ECUs (external control units) and an alternator.
One conventional example of data communication control methods between ECUs and an alternator is disclosed in Japanese Unexamined Patent Publication No. 2002-325085. The communication method disclosed in the Publication establishes bus line connections between ECUs and an alternator, and allows the ECUs to communicate a plurality of information codes with the alternator through the bus lines.
When data communication control methods are applied to communications between a charging generator and a voltage regulator of a voltage regulating apparatus, it is necessary to convert the alternator output into an information code (digital value). Similarly, when data communication control methods are applied to communications between a current generator and a voltage regulator of a battery recharging system for automobiles, it is also necessary to convert the output of the current generator into an information code (digital value).
For these reasons, in order to use the data communication control methods, the alternator or the current generator has to provide an A/D (Analog to Digital) converting circuit for converting the output of the alternator or the current generator into an information code. Installation of the A/D converter into the alternator or the current generator may however contribute to increase of the commit size of the alternator or the current generator, which may cause the voltage regulating apparatus and the battery recharging system to increase in size and cost.